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"We have never before seen an object free-floating in space that looks like this," said Dr. Michael Liu of the Institute for Astronomy at the University of Hawaii at Manoa, who led the international team that discovered the planet.

"It has all the characteristics of young planets found around other stars, but it is drifting out there all alone. I had often wondered if such solitary objects exist, and now we know they do."

While about a thousand planets have been discovered outside our solar system in the past decade by indirect means -- such as observing the wobbling or dimming of their host stars as they orbit -- only a handful of new planets have been directly imaged, all of them around young stars, according to a release from the Institute for Astronomy.

Young stars are those less than 200 million years old.

PSO J318.5-22's solitary existence and its similarity to those directly observed planets makes it a rare find.

"Planets found by direct imaging are incredibly hard to study, since they are right next to their much brighter host stars. PSO J318.5-22 is not orbiting a star so it will be much easier for us to study," said Dr. Niall Deacon of the Max Planck Institute for Astronomy in Germany and a co-author of the study.

"It is going to provide a wonderful view into the inner workings of gas-giant planets like Jupiter shortly after their birth."

The astronomers stumbled across it as they sifted through a mountain of data produced by the Pan-STARRS 1 (PS1) wide-field survey telescope on Haleakala, Maui.